Tailoring thermal conduction in anatase TiO2

• Published in: Communications physics Vol. 2; no. 1
• Main Authors: Mettan, X., Jaćimović, J., Barišić, O. S., Pisoni, A., Batistić, I., Horváth, E., Brown, S., Rossi, L., Szirmai, P., Farkas, B., Berger, H., Forró, L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.10.2019
• Subjects: 639/301/119/995; 639/4077/4107; 639/766/119/995; Physics; Physics and Astronomy
• ISSN: 2399-3650; 2399-3650
• DOI: 10.1038/s42005-019-0224-7

Thermal conductivity ( κ ) plays an essential role in functional devices. It is advantageous to design materials where one can tune κ in a wide range according to its function: single-crystals and nanowires of anatase polymorph of titanium dioxide, broadly used in applications ranging from photovoltaics, reflective coatings to memristors, have been synthesized in large quantities. Here we identify a new, strong diffusion mechanism of heat by polaronic structures due to oxygen vacancies, which considerably influences both the absolute value and the temperature dependence of κ . The additional decrease of κ is achieved in anatase nanowires organized into foam, where porosity and the quasi-one-dimensional size-effect dramatically hinder the propagation of heat, resulting in an extremely low κ  = 0.014 W/Km at room-temperature. Doping this anatase foam could herald promising applications, in particular in thermoelectricity. The thermal properties of a material often determine its suitability for application and use in devices. Here, the thermal conductivity of anatase TiO 2 is tuned over three orders of magnitude from bulk crystals to foam samples, by controlling polaronic effects and texturing.